The present invention relates to a microcapsule system for environment-induced release of active agents.
xe2x80x9cEnvironment-inducedxe2x80x9d is understood to mean, here and below, that the walls of the capsules of the microcapsule system comprise a material which becomes unstable under the influence of one or more specific environmental parameters, such that the corresponding capsules become permeable or burst open and release the active agent optionally contained therein. Examples of such environmental parameters are pressure, temperature, deformation, light and other electromagnetic radiation, particulate radiation, chemical substances etc. Time should also be viewed as an environmental parameter for the purposes of the invention.
Such a microcapsule system is known from DE 40 00 920 A1, for example. In said patent, microcapsules filled with skin care oil are applied to the surface of a cloth. In this way, the skin care oil is protected against evaporation during storage of the cloth. If the cloth is rubbed against the skin, for example, the capsule walls burst as a result of deformation, such that the skin care oil contained in the capsules is released into the surrounding area and may perform its action on the skin of the user.
However, in many instances of use, it may be desirable for not all the active agents to be released at once, but for release of the active agents from the respective microcapsules to proceed in a specific sequence over time.
This object is achieved by a microcapsule system for environment-induced release of active agents, comprising a plurality of capsules having a capsule wall comprising an environment-induced material, an active agent being contained in at least some of the capsules, wherein the plurality of capsules are accommodated in at least one outer capsule and thus form an inner encapsulation layer and the capsule wall of the outer capsule likewise comprises an environment-induced material and the outer capsule forms an outer encapsulation layer.
Through the xe2x80x9cencapsulationxe2x80x9d provided according to the invention of inner capsules in at least one outer capsule, it is possible to achieve sequential release of the active agents, i.e. release occurring in stages over time. The active agents stored in the microcapsule system are thus not necessarily released at once from the respective microcapsules, but rather in a freely selectable sequence over time. This opens up numerous new possibilities, precisely adaptable to the respective requirements, for use of the microcapsule system according to the invention.
Advantageous modifications of the invention are indicated in subclaims.
A modification of the invention increases the number of possible stages over time. The number of possible encapsulation stages is limited only by the maximum possible size of the capsules of the outermost encapsulation layer, which may vary from one application to another.
It is possible to release relatively large amounts of active agent from an encapsulation layer at the same time when said encapsulation layer is broken open.
Complex release sequences for the active agents contained in the capsules of an encapsulation layer may be achieved by two modifications of the invention.
In many instances, it is desirable to release not the same but different active agents in sequence.
The encapsulation layers can be broken open from the outside inwards. The active agents are thus not merely released from the corresponding capsules in sequence, but also discharged into the surrounding area in sequence.
In a modification of the invention, breaking open proceeds in the opposite direction, i.e. from the inside outwards. This is particularly advantageous if, for example, different active agents are firstly to be mixed together before the outermost encapsulation layer is broken open and the active agent mixture thus produced is released to the surrounding area.